No heat main floor. Found system with pressure switch error. Blew through vacuum tube system started. Found cracked heat exchanger, high amp draw on inducer, pressure switch continued to error out. Pressure switch error caused by cracks heat up allowing gases to escape into home as system was leaking carbon monoxide into home. Blower is dirty, no flood protection and system has single wall flue pipe. Quoted repairs advised customer to not operate system due to leaking carbon monoxide and safety concerns associated with that. Left thermostat in off position. Customer getting quote to replace system on Friday 12-26 at 1pm.